The present invention relates to an image processor and an image processing system. More particularly, the invention relates to an image processing technology capable of efficient red-eye correction in so-called direct printing in an image processor which receives image data from an image input apparatus, an image processor connected to an image output apparatus, or an image processing system composed of a combination of these processors.
Conventionally, printing of an image photographed on a photographic film such as a negative film or a reversal film on a photosensitive material (printing paper) is performed by so-called direct exposure in which an image on a film is projected onto a photosensitive material.
In recent years, a digital photo printer has been commercialized. In the digital photo printer, the image recorded on a film is read photoelectrically and converted to digital signals or digital image data is captured with a digital camera; the digital signals or the digital image data is subjected to various image processing operations (digital processing) to produce image data for recording purposes; recording light that has been modulated in accordance with the image data is used to expose a photosensitive material and the exposed photosensitive material is output as a print.
Such image processing based on digital (signal) processing makes it possible to correct colors and densities advantageously and to perform image processing that has been basically impossible to achieve by the conventional direct exposure, as exemplified by gradation correction and sharpening (sharpness enhancement). A high-quality image can be thus obtained.
The most important factor which determines the quality in a photograph of a person-containing image such as a portrait is how the person is finished. Thus, the red-eye effect or appearance of red eyes (pupils) on a photograph caused by flash photography considerably degrades the quality of the photograph and presents a problem.
The red-eye effect often occurs when a person is photographed by using an electronic flash from the front especially in a dark place or in the nighttime. The red-eye-effect takes place in the following way: light of an electronic flash impinges on eyes of a person with pupils open from the front in a dark place, and the electronic flash light is regularly reflected, which state appears in the image. The red-eye effect includes red-eye where pupils are red and gold-eye where pupils are gold. In the following description, red-eye refers to both cases.
In order to suppress the red-eye effect, a camera having a preliminary flash-firing function has been developed in which an electronic flash is preliminarily fired prior to photographing to reduce the opening of the pupils which may cause red-eye effect and thereafter electronic flash photography is performed. However, preliminary firing of an electronic flash cannot always prevent red-eye from occurring depending on the personal differences between subject persons and differences between photographing conditions.
There have also been proposed various methods with which a red-eye image is corrected by the digital image processing as described above to produce an image free from red-eye.
For example, a red-eye correction method is known in which red pupils are converted to pupils of a predetermined color in an image in which red-eye occurred at the time of photographing, by setting the area of red-eye correction through automatic extraction of only red eyes from the region containing red eyes as specified by an operator, or in the case where the automatic extraction of only red eyes is not possible, setting the area of red-eye correction through manual designation of only red eyes by the operator. (for example refer to JP 2001-148780 A).
Another method is also known in which a preliminary image photographed with preliminary firing of an electronic flash is compared with an image photographed with subsequent firing of an electronic flash to detect red-eye in the latter image and the detected red-eye is corrected through conversion to have a predetermined hue, thereby automatically performing red-eye correction in a digital camera (for example, refer to JP 2003-179807 A).
Conventionally, when an image photographed with a digital camera was to be printed, the image data was transferred to a personal computer (PC), where the image data was converted to a printing format suitable for a printer used and sent to the printer for the subsequent printing.
In recent years however, so-called direct printing becomes popular in which image data is directly transferred from a digital camera to a printer without using a PC and is processed and output as a print in the printer. There is well known a system in which, in direct printing using an image supply device such as a digital camera and a printing device such as a printer, image processing is adaptively shared between the devices in accordance with the throughput, data size and data transfer speed per image processing function of each device, in order to perform efficient direct printing (for example, refer to JP 2001-275066 A).
It is also desirable to output a red-eye-corrected, high-quality print as described above in such a direct printing.
However, the conventional red-eye correction methods described in JP 2001-148780 A and JP 2003-179807 A do not support direct printing but requires manual operation by an operator or PC-based processing. In the case where these methods are used in an image processing system performing direct printing, the processing efficiency is not always high.
Although the method described in JP 2001-275066 A shares image processing between devices in direct printing, this document does not disclose specifically how to perform red-eye correction in direct printing.
In any way, it seems that direct printing in which image data can be directly transmitted from a digital camera to a printer without using a PC to quickly perform printing becomes more popular and it has been desired for red-eye correction to be performed more efficiently also in direct printing.